1. Field of the Invention
This invention relates to a method and device for installing a flange on the end of a plastic pipe and to an improved tubular member lined with a plastic pipe liner having such a flanged end.
2. Description of the Prior Art
The installation of plastic pipe liners within tubular members provides several advantages. For example, such liners are used to repair pipelines which have developed cracks or leak points through which conveyed fluid is lost. Such liners are also used to protect metal pipelines from internal corrosion resulting from the corrosive nature of the conveyed fluid.
The plastic pipe liners which have been installed within metal tubular members are usually thermoplastic materials. These materials can be heated to a temperature and for a time sufficient to render the material to a malleable state and to allow components thereof to be fused together. The term "plastic" is intended to include, for example, polyethylene, polyvinylchloride, polyvinylchloride acetate, polystyrene, and the like. Traditionally, the weakest part of the lined pipe system has been the flanged end portions. Various adapters have been provided in the past for joining sections of the pipeline as well as the associated sections of plastic liners. In one prior art technique, adapters were fused onto the plastic liner ends which protruded from the section of metallic pipeline while the liner was in a downsized state. Since the adapters were of a fixed length, it was necessary to accurately calculate the expansion and contraction characteristics of the plastic liner installed within the section of metallic pipeline to prevent the adapter from being pulled out of position upon contraction of the liner as the liner returned to its relaxed state.
In other prior art techniques, an exposed portion of the plastic liner was bent backward at an angle or "flared" to form a flange on the plastic liner. U.S. Pat. No. 3,142,868, to Blount, issued Aug. 4, 1964, is typical of this type prior art approach in which a mechanical device is utilized to flare a liner end extending from a metallic, tubular member. The process also involved heating, supporting and cooling the flared end.
The prior art techniques all suffer from the shortcoming that the liner flanged end could be drawn longitudinally inward into the interior of the tubular member upon contraction of the liner material. Flaring also created thin wall regions at the flanged end which were subject to shearing and failure.
The present invention has as its object to provide a method and device for forming a flange on an end of a plastic pipe liner which resists the tendency to contract, once installed, and be pulled into the interior of the surrounding tubular member.
Another object of the invention is to provide a simple and economical method for forming such a flange on a plastic pipe liner used to line a tubular member.